Enhanced fuse configurations for low-voltage flash memories

ABSTRACT

An enhanced fuse circuit is discussed that advances redundancy techniques in integrated circuits. The enhanced fuse circuit uses a single nonvolatile fuse and a latch that is coupled at a desired time. One embodiment of the invention discusses a fuse circuit that includes a volatile latch and a nonvolatile fuse. The nonvolatile fuse adapts to operate with a voltage supply greater than about 1.65 volts. The voltage supply is boosted at a desired time to a predetermined level and for a predetermined duration so that the nonvolatile fuse transfers its data to the volatile latch.

TECHNICAL FIELD

[0001] The present invention relates generally to semiconductorintegrated circuits. More particularly, it pertains to fuseconfigurations that are used in redundancy circuits in low-voltage flashmemory devices.

BACKGROUND

[0002] Memory devices are integrated circuits in which information maybe stored and from which information may be extracted when desired. Eachmemory device is built from a plurality of memory cells. Each memorycell memorizes a bit of data. Although a bit of data seemsinsignificant, it may determine whether the stored information iscorrect, such as an amount in a bank account.

[0003] A memory cell may become defective because of imperfectmanufacturing practices or degradation over time. Such defects renderthe memory device inoperative or unreliable. Instead of ridding memorydevices with defective memory cells, the semiconductor industry turns tovarious techniques to salvage these memory devices.

[0004] One technique employs redundancy circuits. Redundancy circuitsinclude a number of nondefective memory cells that can replace defectivememory cells in memory devices. Redundancy circuits do not physicallyreplace the defective memory cells but logically replace them.Redundancy circuits detect whether defective memory cells exist,configure memory devices to avoid the defective memory cells, andredirect memory accesses from the defective memory cells to thenondefective memory cells.

[0005] The act of configuring uses fuse circuits, which include fusesthat can be blown to support the act of configuring. Previousgenerations of fuse circuits are incompatible with the memory devices oftoday, which use voltage supplies as low as 1.65 volts. Certain previousgenerations of fuse circuits also tightly integrate fuses and latches.Such integration causes inflexibility that is undesirable.

[0006] Thus, what is needed are devices and methods to enhance fusecircuit configurations in low-voltage integrated circuits, such as flashmemory devices.

SUMMARY OF THE INVENTION

[0007] The above mentioned problems with fuse circuits and otherproblems are addressed by the present invention and will be understoodby reading and studying the following specification. Devices and methodsare described which accord these benefits.

[0008] In one illustrative embodiment, a fuse circuit is discussed. Thefuse circuit includes a volatile latch and a nonvolatile fuse that isreceptive to a voltage supply of about 1.65 volts. The voltage supply isboosted at a desired time to a predetermined level and for apredetermined duration so that the nonvolatile fuse transfers its datato the volatile latch.

[0009] In another illustrative embodiment, a fuse circuit is discussed.The fuse circuit includes an input stage and a nonvolatile fuse having afirst, a second, and a third connection. The first connection receivesan enabling signal. The enabling signal can be boosted so that thenonvolatile fuse selective transfers its data. The input stage isreceptive to an enabling signal.

[0010] In another illustrative embodiment, a fuse circuit is discussed.The fuse circuit includes an input stage that presents an invertedenabling signal, a boosting stage receptive to a boosting signal, and anonvolatile fuse. The nonvolatile fuse has a first, a second, and athird connection. The first connection receives the inverted enablingsignal. The inverted enabling signal is boosted by the boosting stage sothat the nonvolatile fuse selectively transfers its data.

[0011] In another illustrative embodiment, a method is discussed forenhancing a fuse circuit in a low-voltage integrated circuit (IC). Themethod includes presenting by an input stage an inverted enablingsignal, boosting by a boosting stage the inverted enabling signal, andtransferring selectively by a nonvolatile fuse. The nonvolatile fuse hasa first, a second, and a third connection. The first connection receivesthe inverted enabling signal that is boosted so that the nonvolatilefuse selectively transfers its data.

[0012] These and other embodiments, aspects, advantages, and features ofthe present invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a block diagram according to an embodiment of theinvention.

[0014]FIG. 2 is a block diagram according to an embodiment of theinvention.

[0015]FIG. 3 is a circuit diagram according to an embodiment of theinvention.

[0016] FIGS. 4A-4E are timing diagrams according to an embodiment of theinvention.

[0017]FIG. 5 is a block diagram according to an embodiment of theinvention.

DETAILED DESCRIPTION

[0018] In the following detailed description of the invention, referenceis made to the accompanying drawings that form a part hereof, and inwhich is shown, by way of illustration, specific embodiments in whichthe invention may be practiced. In the drawings, like numerals describesubstantially similar components throughout the several views. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention. Other embodiments may be utilizedand structural, logical, and electrical changes may be made withoutdeparting from the scope of the present invention.

[0019] The transistors described herein include transistors frombipolar-junction technology (BJT), field-effect technology (FET), orcomplementary metal-oxide-semiconductor (CMOS) technology. Ametal-oxide-semiconductor (MOS) transistor includes a gate, a first node(drain) and a second node (source). Since a MOS is typically asymmetrical device, the true designation of “source” and “drain” is onlypossible once voltage is impressed on the terminals. The designations ofsource and drain herein should be interpreted, therefore, in thebroadest sense.

[0020] The terms “high” and “low” as used herein refer to Vcc, thevoltage supply, and ground, respectively. The term “external supply” asused herein refers to Vcc, the voltage supply. In one embodiment, thevoltage supply supplies a voltage in the range of 1.65 to 2.22 volts,unless otherwise indicated.

[0021] The term “energy-storing device” described herein includes anydevices capable of storing charges. The term “energy-storing device”includes a capacitor. The capacitor described herein can be anycapacitor fabricated on an integrated circuit using any fabricationtechnique. The energy-storing device described herein, however, may befabricated as either an n-channel transistor or a p-channel transistor;the transistor's source and drain are connected together to form oneconductive plate, its gate forms the other conductive plate, and theoxide layer forms the dielectric.

[0022] The term “pre-charging device” described herein includes anydevices capable of providing charges to maintain a predetermined levelof charges in an energy-storing device while a system that includes theenergy-storing device is turned off. The reason for pre-charging isthus: the energy-storing device may have to store a large amount ofcharges to enable a circuit to provide a high-voltage signal. Withoutpre-charging, an undesired amount of time may have to be taken once thesystem is turned on to charge the energy-storing device. Thepre-charging device described herein can be a square-law device. Thepre-charging device described herein can be any transistor fabricated onan integrated circuit using any fabrication technique. The pre-chargingdevice described herein, however, may be fabricated as an n-channeltransistor with its drain and gate connected together; the drain isconnected to an external supply.

[0023] The term “charging device” described herein includes any devicescapable of charging an energy-storing device up to the level of theexternal supply. The purpose of the charging device is to charge theenergy-storing device to compensate for any level degradation that mayoccur from the pre-charging process. The charging device describedherein can be any transistor fabricated on an integrated circuit usingany fabrication technique. The charging device described herein,however, may be fabricated as an n-channel transistor. This transistormay be configured with its drain connected to an external supply.

[0024] The embodiments of the invention focus on a fuse circuit that isemployed in redundancy circuits. The fuse circuit of the embodiments ofthe invention uses memory cells as fuses. This is advantageous becausememory cells are basically transistors that can be controlled. Thisability to control the memory cells as fuses to set or to unset thefusing state is not possible with traditional fuses. Once a state of atraditional fuse is set, such as by blowing or melting, the state of thetraditional fuse cannot be reversed.

[0025] Additionally, the memory cells can be used as trimming elements.Trimming elements fine-tune a configuration of integrated circuits, suchas flash memory devices. Again, the process of fine-tuning an integratedcircuit can be reversed with the memory cells as trimming elements.

[0026] Integrated circuits, such as flash memory devices, haveprogressed from being included in personal computers to handheldproducts, such as wireless phones. The marketplace values handheldproducts that are based on low-voltage integrated circuits, such asflash memory devices, because such products use less power and thereforelast longer. Handheld products need to store information, andlow-voltage flash memory is chosen as a storage medium. Low-voltageflash memory uses voltage supplies as low as 1.65 volts. Previousgenerations of fuse circuits rely on voltage supplies that provide highvoltages. Thus, they are incompatible with low-voltage integratedcircuits. In the discussion below, the embodiments of the inventionsolve these and other problems.

[0027]FIG. 1 is a block diagram of a system according to one embodimentof the invention. An integrated circuit 100 illustrates a portion of alow-voltage flash memory device 102. The low-voltage flash memory device102 includes a voltage supply 104 and ground 112. The voltage supply 104provides voltages as low as about 1.65 volts and as high as about 2.2volts. This range of voltages is less than voltages used in previousgenerations of flash memory devices. The voltage supply 104 providespower to circuits within the portion of the low-voltage flash memorydevice 102.

[0028] The low-voltage flash memory device 102 includes a decoder 106.The decoder 106 receives address signals from another integratedcircuit, such as a central processing unit, that wants to access thelow-voltage flash memory device 102. The decoder 106 decodes the addresssignals into an access signal that can select a memory cell or a groupof memory cells so as to retrieve or store desired information.

[0029] The low-voltage flash memory device 102 includes an array 110.The array 110 houses a plurality of memory cells. Each of the pluralityof memory cells is selectable by the decoder 106. The array 110typically arranges the memory cells into rows and columns. To select amemory cell in the array 1 10, the decoder provides a specific row and aspecific column. In the idioms of computer architecture, the row iscalled a word line and the column is called a bit line.

[0030] The low-voltage flash memory device 102 includes a redundancycircuit 108. The redundancy circuit 108 is modified by at least oneembodiment of the invention to work with low voltages provided by thevoltage supply 104. The redundancy circuit 108 provides redundant memoryelements that can logically replace defective memory elements in thearray 110.

[0031]FIG. 2 is a block diagram of a redundancy circuit according to oneembodiment of the invention. A redundancy circuit 200 includes a portionof a row fuse bank 208 and a column fuse bank 216. The row fuse bank 208provides logical replacement for defective memory cells along a row ofan array. The row fuse bank 208 includes a fuse circuit 204. The fusecircuit 204 includes the fuses and other elements that may provide theconfiguration needed to logically replace memory cells along a row of anarray. The fuse circuit 204 includes various modifications provided byat least one embodiment of the invention.

[0032] The row fuse bank 208 includes a match circuit 206. The matchcircuit 206 includes a group of logic devices. This group of logicdevices act together to emulate a logic function that produces a rowmatch signal. This row match signal reflects whether a row in the arrayshould be replaced because it contains at least one defective memorycell.

[0033] The row fuse bank 208 includes a disable circuit 202. Apossibility exists that the fuse circuit 204 may include fuses that aredefective. The disable circuit 202 disables the fuse circuit 204 if itdetects that the fuse circuit 204 is unreliable.

[0034] The redundancy circuit 200 includes the column fuse bank 216. Thecolumn fuse bank 216 includes circuitry that is common to circuitry inthe row fuse bank 208. The column fuse bank 216 provides logicalreplacement for defective memory cells along a column of an array. Thecolumn fuse bank 216 includes a fuse circuit 212. The fuse circuit 212includes the fuses and other elements that may provide the configurationneeded to logically replace memory cells along a column of an array. Thefuse circuit 212 includes various modifications provided by at least oneembodiment of the invention.

[0035] The column fuse bank 216 includes a match circuit 214. The matchcircuit 214 includes a group of logic devices. This group of logicdevices act together to emulate a logic function that produces a columnmatch signal. This column match signal reflects whether a column in thearray should be replaced because it contains at least one defectivememory cell.

[0036] The column fuse bank 216 includes a disable circuit 210. Apossibility exists that the fuse circuit 212 may include fuses that aredefective. The disable circuit 210 disables the fuse circuit 212 if itdetects that the fuse circuit 212 is unreliable.

[0037]FIG. 3 is a circuit diagram according to one embodiment of theinvention. A fuse circuit 300 includes a transferring stage 330. Onepurpose of the transferring stage 330 includes transferring the state ofthe fuse to another circuit. This serves to partially decouple the fusefrom another circuit. The transferring stage 330 receives a transferringsignal S302 and presents the transferring signal S302 at node A. Thetransferring stage 330 includes an inverter I304. The inverter I304receives the transferring signal S302, produces an inverted transferringsignal, and presents the inverted transferring signal to a node B.

[0038] The transferring stage 330 includes a p-channel transistor T306having a gate, a drain, and a source. The gate of the p-channeltransistor T306 couples to the node B. The source of the p-channeltransistor T306 couples to a supply voltage. The drain of the p-channeltransistor T306 couples to a node C.

[0039] The transferring stage 330 includes an n-channel transistor T318having a gate, a drain, and a source. The gate of the n-channeltransistor T318 couples to the node B. The drain of the n-channeltransistor T318 couples to the node C. The source of the n-channeltransistor T318 couples to the nonvolatile fuse 334, which will bediscussed.

[0040] The fuse circuit 300 includes a latch L312. One purpose of thelatch is to memorize the state of the fuse until the latch is notifiedotherwise. In one embodiment, the latch L312 is a volatile latch. Inanother embodiment, the latch L312 includes an inverter I308 having aninput connection and an output connection. The input connection of theinverter I308 couples to a node D, and the output connection of theinverter I308 couples to the node C. The latch L312 also includesanother inverter I310 having an input connection and an outputconnection. The input connection of the inverter I310 couples to thenode C, and the output connection of the inverter I310 couples to thenode D.

[0041] The fuse circuit 300 produces the signal S314 and presents thesignal at the node D. This signal S314 reflects the state of the fuse ofthe fuse circuit 300.

[0042] The fuse circuit 300 includes a boosting stage 336. The boostingstage 336 boosts the voltage supply at a desired time to a predeterminedlevel and for a predetermined duration. The boosting stage 336 includesan inverter I316 having an input connection and an output connection.The input connection of the inverter I316 couples to the node A, andtherefore, is receptive to the transferring signal S302. The outputconnection of the inverter I316 presents a boosting signal.

[0043] The boosting stage 336 includes an energy-storing device C330having a first connection and a second connection. In one embodiment theenergy-storing device C330 is a capacitor with a value of about 10picofarads. The first connection of the energy-storing device C330receives the boosting signal from the inverter I316. The secondconnection of the energy-storing device C330 couples to a node G.

[0044] The fuse circuit 300 includes a nonvolatile fuse 334 having afirst, a second, and a third connection. The first connection of thenonvolatile fuse 334 couples to the node G. The second connection of thenonvolatile fuse 334 couples to the source of the n-channel transistorT318 of the transferring stage 330. The third connection of thenonvolatile fuse 334 couples to ground.

[0045] In one embodiment, the nonvolatile fuse 334 is a flash cell T332having a gate, a drain, and a source. The gate of the flash cell T332couples to the node G. The drain of the flash cell T332 couples to thesource of the n-channel transistor T318 of the transferring stage 330.The source of the flash cell T332 couples to ground. In one embodiment,the threshold voltage of the flash cell is greater than about 2.5 voltsand less than about 3.5 volts. In one embodiment, the flash cell T332refrains from transferring its data to the latch L312 when the flashcell T332 is in a programmed state if the gating signal at the gate ofthe flash cell is sufficiently high. In another embodiment, the flashcell T332 transfers its data when the nonvolatile fuse is in an erasedstate if the gating signal at the gate of the flash cell T332 issufficiently high.

[0046] The fuse circuit 300 includes an input stage 338. The input stage338 receives an enabling signal S320, and presents the enabling signalS320 to an inverter I322. The inverter I322 includes an input connectionand an output connection. The input connection of the inverter I322receives the enabling signal S320, and the output connection of theinverter I322 presents a gating signal at a node E.

[0047] Also coupled to the node E is an n-channel transistor T328 havinga gate, a drain, and a source. In one embodiment, the n-channeltransistor T328 includes a threshold voltage that is less than I volt.The gate of the n-channel transistor T328 couples to the node F. Thedrain of the n-channel transistor T328 couples to the node E. The sourceof the n-channel transistor T328 couples to the node G. The n-channeltransistor T328 receives the gating signal at the drain, and presentsthe gating signal at the node G if the n-channel transistor is turnedon.

[0048] The input stage 338 includes a pre-charging device T326. In oneembodiment, the pre-charging device T326 is an n-channel transistorhaving a gate, a drain, and a source. The gate of the pre-chargingdevice T326 couples to the drain and the drain of the pre-chargingdevice T326 couples to the voltage supply. The source of thepre-charging device T326 couples to the node F.

[0049] The input stage 338 includes an energy-storing device C324 havinga first connection and a second connection. In one embodiment, theenergy-storing device C324 includes a capacitor with a value of about0.1 picofarad. The first connection of the energy-storing device C324couples to the node E. The second connection of the energy-storingdevice C324 couples to the node F.

[0050] The pre-charging device T326 pre-charges the energy-storingdevice C324. Current flows from the voltage supply, through the drain ofthe pre-charging device T326, through the source of the pre-chargingdevice T326, and enters the energy-storing device C324 at the node F.Because a certain amount of charge is diverted to the gate of thepre-charging device T326 to turn on the pre-charging device T326, thepre-charged charges at the energy-storing device C324 are equivalent tothe difference between the voltage supply and the threshold voltage ofthe pre-charging device T326.

[0051] The purpose of pre-charging the energy-storing device C324 is toboost any signal that is presented at the node E, so that the n-channeltransistor T328 presents the signal at the node G without degradation.For example, suppose the inverter I322 presents a gating signal at thenode E. Without the pre-charged energy-storing device C324, then-channel transistor T328 presents the gating signal at the node G at avoltage level that is less than the voltage level of the gating signalpresented at the node E. The difference in the voltage level isapproximately the threshold voltage of the n-channel transistor T328.

[0052] The operation of the fuse circuit 300 progresses over at leastthree phases. In the first phase, at power up, the transferring signalS302 and the enabling signal S320 is at a high level. Because thetransferring signal S302 is at a high level, the node A is at a highlevel. The inverter I304 inverts the transferring signal S302 andpresents a switching signal at a low level at the node B. The switchingsignal, at the low level, turns on the p-channel transistor T306 andturns off the n-channel transistor T318. The turned-on p-channeltransistor T306 switches the node C to the voltage supply, so that thenode C is at a high level. The inverter I310 inverts the voltage at thenode C, which is at a high level, to produce the signal S314 at a lowlevel.

[0053] Returning to node A, which is at a high level, the inverter I316inverts the voltage at the node A and presents a boosting signal at alow level. Turning now to node E, the inverter I322 inverts the enablingsignal S320, which is at a high level, to present a gating signal at alow level to the node E. The n-channel transistor T328 presents thegating signal at the low level to the node G. Because both the boostingsignal and the voltage at the node G is low, the energy-storing deviceC330 does not charge up. Additionally, the voltage at the node G is toolow to turn on the nonvolatile fuse 334.

[0054] In the second phase, the transferring signal S302 remains at ahigh level, but the enabling signal S320 changes to a low level. Withthe transferring signal S302 at a high level, the transferring stage andthe latch L312 maintain the same state as discussed hereinbefore. Thus,the latch L312 couples to the voltage supply, and continues to presentthe signal S314 at a low level. The boosting signal remains at a lowlevel.

[0055] With the enabling signal S320 now at a low level, the inverterI322 presents the gating signal at a high level at the node E. Theenergy-storing device C324 boosts the gating signal even higher. Then-channel transistor T328 presents the gating signal at approximatelythe level of the voltage supply at the node G. The current of the gatingsignal flows to the energy-storing device C330, and over time chargesthe energy-storing device C330 up to the level of the gating signal,which is about the level of the voltage supply. The voltage of thegating signal at the node G at this point is still insufficient to turnon the nonvolatile fuse 334.

[0056] In the third phase, the transferring signal S302 changes to thelow level while the enabling signal S320 remains at the low level. Thetransferring signal S302 is presented at the node A at the low level.The inverter I304 inverts the transferring signal S302 and presents aswitching signal at a high level at the node B. The switching signal,which is at a high level, turns off the p-channel transistor T306 andturns on the n-channel transistor T318. The turned-off p-channeltransistor switches the node C from the voltage supply. The turned-onn-channel transistor T318 switches the node C to the nonvolatile fuse334.

[0057] Returning to the node A, the inverter I316 receives thetransferring signal, which is at a high level, and presents the boostingsignal at a high level to the energy-storing device C330. Recall thatthe energy-storing device C330 is already charged to a high level. Thepresence of the boosting signal at the high level boosts the amount ofcharges stored in the energy-storing device C330 to an even higherlevel. This boosted amount of charges is equivalent to twice the levelof the gating signal at the node G. This level of the gating signal isgreater than the threshold voltage of the nonvolatile fuse 334 and issufficient to turn on the nonvolatile fuse 334. In one embodiment, thethreshold voltage of the nonvolatile fuse 334 is greater than about 2.5volts and less than about 3.5 volts.

[0058] The boosted gating signal at the node G will decay over time. Thecharges that are stored in the energy-storing device C330 escape throughthe source of the n-channel transistor T328 to enter the substrate ofthe n-channel transistor T328. However, the gating signal is boosted fora sufficient duration so that the nonvolatile fuse 334 selectivelytransfers its data to the latch L312.

[0059] In the embodiment in which the nonvolatile fuse 334 is a flashcell, the nonvolatile fuse 334 pulls the node C to ground if thenonvolatile fuse is in an erased state. With the voltage at the node Cat a low level, the inverter I310 presents the signal S314 at a highlevel. If the nonvolatile fuse 334 is in a programmed state, the boostedgating signal is still insufficient to turn on the nonvolatile fuse 334.Thus, the node C is not coupled to the voltage supply or to ground.However, the latch L312 remembers the previous voltage level at the nodeC, which was high, and continues to produce a signal S314 at a lowlevel.

[0060] FIGS. 4A-4E are timing diagrams according to one embodiment ofthe invention. These timing diagrams reflect voltages of varioussignals, nodes, and components of the fuse circuit 300 as discussedhereinbefore. The abscissa of each of the timing diagrams representstime. Each tick (major and minor) of the abscissa is spaced 25nanoseconds apart. The ordinate of each of the timing diagram representsvoltages. Each tick of the ordinate is spaced 500 millivolts apart. Theunits and the increments of the units used in the abscissa and theordinate are for illustrative purposes only-they should not beinterpreted as limitations upon the embodiments of the invention. Thetransitions of the waveforms of the timing diagrams are also forillustrative purposes only—they should not be interpreted as limitationsupon the embodiments of the invention.

[0061] In various embodiments discussed above, the boosting stage isused to boost the gating signal to a level to turn on the nonvolatilefuse 334. In another embodiment, the boosting stage is replaced with asignal elsewhere to boost the gating signal; that signal may come from acharge-pump circuit, for example.

[0062]FIG. 4A illustrates a timing diagram for the transferring signalS302. At 0 nanoseconds (at power up), the transferring signal S302 ishigh. The transferring signal S302 remains high until 300 nanosecondselapse at which time the transferring signal S302 changes to low. Thetransferring signal S302 then remains low.

[0063]FIG. 4B illustrates a timing diagram for the enabling signal S320.The enabling signal S320 is initially high at 0 nanoseconds (at powerup). The enabling signal S320 remains high until 100 nanoseconds elapseat which timethe enabling signal changes to low. The enabling signalS320 then remains low.

[0064]FIG. 4C illustrates a timing diagram for the gating signal at thenode G. The gating signal is at a low level from 0 nanoseconds to 100nanoseconds because the energy-storing device C330 has not charged up.When the enabling signal S320 changes to low at 100 nanoseconds, thegating signal at the node G begins to rise because the energy-storingdevice C330 is now charging up. The gating signal continues to riseuntil, at 300 nanoseconds, the gating signal reaches a certain voltagelevel. Also at 300 nanoseconds, the transferring signal S302 drops to alow voltage level. In turn, the gating signal is boosted to a highervoltage level. The gating signal then remains at the higher voltagelevel.

[0065]FIG. 4D illustrates a timing diagram for the voltage level at thenode C. At 0 nanoseconds (at power up), the voltage level at the node Cpulls up to the voltage supply as discussed hereinbefore. When thetransferring signal S302 changes to a low level at about 300nanoseconds, the voltage level at the node C switches to ground if thenonvolatile fuse 334 is turned on. Hence, the voltage at the node C islow.

[0066]FIG. 4E illustrates a timing diagram for the voltage level at thenode D. The timing diagram also reflects the voltage level of the signalS314. The waveform of the timing diagram of the FIG. 4E is an inversionof the waveform of the timing diagram of the FIG. 4D due to the inverterI310. Thus, from 0 nanoseconds to 300 nanoseconds, the voltage level ofthe signal S314 is low. Afterward, the timing diagram shows the voltagelevel of the signal S314 is high.

[0067]FIG. 5 is a block diagram according to one embodiment of thepresent invention. A wireless device 500 includes a display 502, anantenna 504, a processor 506, and a low-voltage flash memory device 508.The display 502 provides a user interface that can be navigated by auser to control the wireless device 500. The processor 506 processesdata and controls provided by the user or a remote server (not shown).The low-voltage flash memory device 508 provides storage to store dataand controls. In one embodiment, the low-voltage flash memory device 508includes at least one embodiment of the invention as discussedhereinbefore. The wireless device 500 includes digital cameras, audiorecorders, personal digital assistants, and test equipment. Thelow-voltage flash memory device 508 is used to store firmware, fonts,forms, data, faxes, digital audio clips, digital images, and so on.

Conclusion

[0068] Systems, devices, and methods have been discussed to enhance fusecircuits in integrated circuits, such as flash memory devices. Onebenefit of the fuse circuits of the embodiments of the invention is thatthe fuse is composed of a nonvolatile transistor. This economizesmanufacturing of the integrated circuits because the integrated circuitsare generally manufactured with millions of transistors already. Anotherbenefit of the embodiments of the invention is that the fuse and thelatch are not integrated; the fuse and the latch couple together for adesired duration so that the fuse can transfer its state onto the latch.Thereafter, the latch remembers and outputs the state of the fuse.

[0069] Although the specific embodiments have been illustrated anddescribed herein, it will be appreciated by those of ordinary skill inthe art that any arrangement which is calculated to achieve the samepurpose may be substituted for the specific embodiments shown. Thisapplication is intended to cover any adaptations or variations of thepresent invention. It is to be understood that the above description isintended to be illustrative, and not restrictive. Combinations of theabove embodiments and other embodiments will be apparent to those ofskill in the art upon reviewing the above description. The scope of theinvention includes any other applications in which the above structuresand fabrication methods are used. Accordingly, the scope of theinvention should only be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

I claim:
 1. A fuse circuit, comprising: a volatile latch; and anonvolatile fuse adapted to operate with a voltage supply greater thanabout 1.65 volts, wherein the voltage supply is boosted at a desiredtime to a predetermined level and for a predetermined duration so thatthe nonvolatile fuse transfers its data to the volatile latch.
 2. Thefuse circuit of claim 1, wherein the nonvolatile fuse includes a flashcell having a threshold voltage of greater than about 2.5 volts and lessthan about 3.5 volts.
 3. The fuse circuit of claim 1, wherein thevolatile latch includes a pair of inverters.
 4. The fuse circuit ofclaim 1, wherein the nonvolatile fuse refrains from transferring itsdata when the nonvolatile fuse is in a programmed state.
 5. The fusecircuit of claim 1, wherein the nonvolatile fuse transfers its data whenthe nonvolatile fuse is in an erased state.
 6. A fuse circuit,comprising: an input stage produces a gating signal; and a nonvolatilefuse having a first, a second, and a third connection, wherein the firstconnection receives the gating signal, and wherein the gating signal isboosted so that the nonvolatile fuse selectively transfers its data. 7.The fuse circuit of claim 6, wherein the input stage includes atransistor having a gate, a drain, and a source, wherein the gatereceives a voltage supply that is greater than about 1.65 volts, whereinthe drain receives an enabling signal, and wherein the source presentsthe gating signal.
 8. The fuse circuit of claim 7, wherein the inputstage includes an inverter having a first and a second connection,wherein the first connection of the inverter receives the enablingsignal, and wherein the second connection presents a gating signal. 9.The fuse circuit of claim 6, wherein the nonvolatile fuse includes athreshold voltage, wherein the gating signal, which is boosted to alevel greater than the threshold voltage, turns on the nonvolatile fuseif the nonvolatile fuse is in an erased state.
 10. The fuse circuit ofclaim 6, wherein the nonvolatile fuse is a flash cell.
 11. A fusecircuit, comprising: an input stage that presents a gating signal; aboosting stage that produces a boosting signal; and a nonvolatile fusehaving a first, a second, and a third connection, wherein the firstconnection receives the gating signal, and wherein the gating signal isboosted by the boosting stage so that the nonvolatile fuse selectivelytransfers its data.
 12. The fuse circuit of claim 11, wherein theboosting stage includes an energy-storing device having a firstconnection and a second connection, wherein the second connection of theenergy-storing device receives the gating signal.
 13. The fuse circuitof claim 12, wherein the boosting stage includes an inverter having afirst and a second connection, wherein the first connection of theboosting stage receives a transferring signal, and wherein the secondconnection presents the boosting signal to the first connection of theenergy-storing device.
 14. The fuse circuit of claim 13, wherein theenergy-storing device stores a first level of energy when the boostingsignal is low and the gating signal is high.
 15. The fuse circuit ofclaim 14, wherein the energy-storing device boosts the first level ofenergy to the second level of energy when the boosting signal is highand the gating signal is high.
 16. A fuse circuit, comprising: an inputstage that presents a gating signal; a boosting stage that produces aboosting signal; a transfer stage receptive to a transferring signal;and a nonvolatile fuse having a first, a second, and a third connection,wherein the first connection receives the gating signal, and wherein thegating signal is boosted by the boosting stage so that the transferstage transfers the data of the nonvolatile fuse.
 17. The fuse circuitof claim 16, wherein the transfer stage includes an inverter having afirst and a second connection, wherein the first connection is receptiveto a transferring signal, and wherein the second connection presents aswitching signal.
 18. The fuse circuit of claim 17, wherein thetransferring stage includes a p-channel transistor having a gate, adrain, and a source, wherein the gate receives the switching signal,wherein the drain receives a voltage supply that is greater than about1.65 volts.
 19. The fuse circuit of claim 18, wherein the transferringstage includes an n-channel transistor having a gate, a drain, and asource, wherein the gate of the n-channel transistor receives theswitching signal, wherein the drain of the n-channel transistor couplesto the source of the p-channel transistor, wherein the source of then-channel transistor couples to the second connection of the nonvolatilefuse.
 20. The fuse circuit of claim 19, wherein the nonvolatile fuseincludes a flash cell having a gate, a drain, and a source, wherein thegate of the flash cell couples to the boosting stage, wherein the drainof the flash cell couples to the source of the n-channel transistor, andwherein the source of the flash cell couples to ground.
 21. A fusecircuit, comprising: an input stage that presents a gating signal; aboosting stage that produces a boosting signal; a transfer stagereceptive to a transferring signal; a latch receptive to data that istransferred by the transfer stage; and a nonvolatile fuse that includesa flash cell having a gate, a drain, and a source, wherein the gatereceives the gating signal, wherein the drain couples to the transferstage, and wherein the source couples to ground.
 22. The fuse circuit ofclaim 21, wherein the input stage receives an enabling signal andpresents the gating signal.
 23. The fuse circuit of claim 22, whereinthe boosting stage receives the gating signal and stores a first levelof energy, and wherein the boosting stage boosts the first level ofenergy to a second level of energy when the boosting signal is high. 24.The fuse circuit of claim 23, wherein the transfer stage switches thelatch to a voltage supply that is greater than about 1.65 volts when thetransferring signal is high, and wherein the transfer stage switches thelatch to the flash cell when the transferring signal is low.
 25. Thefuse circuit of claim 24, wherein the flash cell transfers its data tothe transfer stage for transferring to the latch when the flash cellreceives the second level of energy from the boosting stage at a levelthat is greater than a threshold voltage.
 26. A method for enhancing afuse circuit in a low-voltage IC, comprising: presenting by an inputstage a gating signal; boosting by a boosting stage the gating signal;and transferring selectively by a nonvolatile fuse having a first, asecond, and a third connection, wherein the first connection receivesthe gating signal that is boosted so that the nonvolatile fuseselectively transfers its data.
 27. The method of claim 26, whereinboosting includes storing by an energy-storing device having a firstconnection and a second connection, wherein the second connection of theenergy-storing device receives the gating signal.
 28. The method ofclaim 27, wherein boosting includes inverting by an inverter having afirst and a second connection, wherein the first connection of theboosting stage receives a transferring signal, and wherein the secondconnection presents the boosting signal to the first connection of theenergy-storing device.
 29. The method of claim 28, wherein storingincludes storing a first level of energy when the boosting signal is lowand the gating signal is high.
 30. The method of claim 29, whereinboosting includes boosting the first level of energy to the second levelof energy when the boosting signal is high and the gating signal ishigh.
 31. A method for enhancing a fuse circuit in a low-voltage IC,comprising: presenting by an input stage a gating signal; boosting by aboosting stage the gating signal; transferring by a transfer stage adata; and providing the data to the transfer stage by a nonvolatile fusehaving a first, a second, and a third connection, wherein the firstconnection receives the gating signal that is boosted.
 32. The method ofclaim 31, wherein transferring includes inverting by an inverter havinga first and a second connection, wherein the first connection isreceptive to a transferring signal, and wherein the second connectionpresents a switching signal.
 33. The method of claim 32, whereintransferring includes switching by a p-channel transistor having a gate,a drain, and a source, wherein the gate receives the switching signal,wherein the drain receives a voltage supply that is greater than about1.65 volts.
 34. The method of claim 33, wherein transferring includesswitching by an n-channel transistor having a gate, a drain, and asource, wherein the gate of the n-channel transistor receives theswitching signal, wherein the drain of the n-channel transistor couplesto the source of the p-channel transistor, wherein the source of then-channel transistor couples to the second connection of the nonvolatilefuse.
 35. The method of claim 34, wherein providing includes providingby a flash cell having a gate, a drain, and a source, wherein the gateof the flash cell couples to the boosting stage, wherein the drain ofthe flash cell couples to the source of the n-channel transistor, andwherein the source of the flash cell couples to ground.
 36. A method forenhancing a fuse circuit in a low-voltage IC, comprising: presenting byan input stage a gating signal; boosting by a boosting stage the gatingsignal; transferring by a transfer stage a data; latching by a latch thedata transferred by the transfer stage; and providing the data by anonvolatile fuse that includes a flash cell having a gate, a drain, anda source, wherein the gate receives the gating signal, wherein the draincouples to the transfer stage, and wherein the source couples to ground.37. The method of claim 36, further comprising receiving an enablingsignal by the input stage, and wherein the act of receiving the enablingsignal precedes the act of presenting the gating signal.
 38. The methodof claim 37, wherein boosting includes receiving the gating signal andstoring a first level of energy, and wherein the act of boosting booststhe first level of energy to a second level of energy when a boostingsignal, which is produced by the boosting stage, is high.
 39. The methodof claim 38, wherein transferring includes coupling the latch to avoltage supply that is greater than about 1.65 volts when a transferringsignal, which is presented to the transfer stage, is high, and whereintransferring includes coupling the latch to the flash cell when thetransferring signal is low.
 40. The method of claim 39, whereinproviding includes providing by the flash cell its data to the transferstage for transferring to the latch when the flash cell receives thesecond level of energy from the boosting stage at a level that isgreater than a threshold voltage.
 41. A fuse bank in a low-voltageintegrated circuit, comprising: a fuse circuit, including: an inputstage that presents an inverted enabling signal; a boosting stage thatproduces a boosting signal; a transfer stage receptive to a transferringsignal; a latch receptive to data that is transferred by the transferstage; a nonvolatile fuse that includes a flash cell having a gate, adrain, and a source, wherein the gate receives the gating signal,wherein the drain couples to the transfer stage, and wherein the sourcecouples to ground; a matching circuit receptive to the data from thelatch to produce a matching signal; and a fuse disabling circuit todisable the fuse circuit if the fuse circuit is impaired.
 42. A wirelessdevice, comprising: a display; a processor; and a flash memory devicethat includes a redundancy circuit having a fuse circuit, the fusecircuit includes: an input stage that presents a gating signal; aboosting stage that produces a boosting signal; a transfer stagereceptive to a transferring signal; a latch receptive to data that istransferred by the transfer stage; and a nonvolatile fuse that includesa flash cell having a gate, a drain, and a source, wherein the gatereceives the gating signal, wherein the drain couples to the transferstage, and wherein the source couples to ground.
 43. A fuse circuitcomprising: a volatile latch; and a nonvolatile fuse to hold data, thenonvolatile fuse being adapted to operate with a voltage supply greaterthan about 1.65 volts, the voltage supply to be boosted to apredetermined level for a predetermined duration to enable thenonvolatile fuse to transfer the data to the volatile latch.
 44. Thefuse circuit of claim 43 wherein: the volatile latch comprises an outputof a first inverter coupled to an input of a second inverter and anoutput of the second inverter coupled to an input of the first inverter;the nonvolatile fuse comprises a flash cell having a threshold voltageof greater than about 2.5 volts and less than about 3.5 volts; thevoltage supply comprises a voltage supply in the range of 1.65 volts to2.22 volts; the voltage supply is to be boosted to about double thevoltage supply by a boost circuit comprising a capacitor coupled to agate of the flash cell; and the boosted voltage is sufficient to turn onthe flash cell if the flash cell is in an erased state and the boostedvoltage is insufficient to turn on the flash cell if the flash cell isin a programmed state.
 45. A fuse circuit comprising: an input stage toproduce a gating signal; and a nonvolatile fuse to hold data, thenonvolatile fuse having a first connection coupled to receive the gatingsignal, a second connection, and a third connection, the gating signalto be boosted to enable the nonvolatile fuse to selectively transfer thedata.
 46. The fuse circuit of claim 45 wherein: the nonvolatile fusecomprises a flash cell comprising a gate coupled to receive the gatingsignal, a drain, and a source coupled to ground, the flash cell having athreshold voltage of greater than about 2.5 volts and less than about3.5 volts; the input stage comprises: a transistor comprising a gate, adrain, and a source, the gate of the transistor being coupled to receivea voltage supply in the range of 1.65 volts to 2.22 volts, the drain ofthe transistor being coupled to receive an enabling signal, and thesource of the transistor being coupled to the gate of the flash cell topresent the gating signal; and an inverter having an input coupled toreceive the enabling signal and an output coupled to the transistor; andthe boosted gating signal is to be boosted from the voltage supply, theboosted gating signal being sufficient to turn on the flash cell if theflash cell is in an erased state and the boosted gating signal beinginsufficient to turn on the flash cell if the flash cell is in aprogrammed state.
 47. A fuse circuit comprising: an input stage topresent a gating signal; a boosting stage coupled to the input stage toboost the gating signal in response to a boosting signal; and anonvolatile fuse to hold data, the nonvolatile fuse having a firstconnection coupled to the input stage to receive the gating signal, asecond connection, and a third connection, the gating signal to beboosted to enable the nonvolatile fuse to selectively transfer the data.48. The fuse circuit of claim 47 wherein: the nonvolatile fuse comprisesa flash cell comprising a gate coupled to receive the gating signal, adrain, and a source coupled to ground, the boosted gating signal beingsufficient to turn on the flash cell if the flash cell is in an erasedstate and the boosted gating signal being insufficient to turn on theflash cell if the flash cell is in a programmed state; the input stagecomprises an inverter coupled in series with a transistor that iscoupled to the gate of the flash cell, the inverter being coupled toreceive an enabling signal, the transistor to generate the gating signalin response to the enabling signal; the boosting stage comprises: aninverter having an input coupled to receive a transferring signal and anoutput to generate the boosting signal; a capacitor having a firstconnection coupled to the output of the inverter to receive the boostingsignal and a second connection coupled to the gate of the flash cell toboost the gating signal, the capacitor to store a first level of energybased on a voltage supply in the range of 1.65 volts to 2.22 volts whenthe boosting signal is low and the gating signal is high and to boostthe first level of energy to a second level of energy when the boostingsignal is high and the gating signal is high.
 49. A fuse circuitcomprising: an input stage to present a gating signal; a boosting stagecoupled to the input stage to boost the gating signal in response to aboosting signal; a transferring stage coupled to receive a transferringsignal; and a nonvolatile fuse to hold data, the nonvolatile fuse havinga first connection coupled to the input stage and the boosting stage toreceive the gating signal, a second connection, and a third connection,the gating signal to be boosted to enable the nonvolatile fuse totransfer the data to the transferring stage.
 50. The fuse circuit ofclaim 49 wherein: the nonvolatile fuse comprises a flash cell comprisinga gate coupled to the input stage to receive the gating signal, a drain,and a source coupled to ground, the boosted gating signal beingsufficient to turn on the flash cell if the flash cell is in an erasedstate and the boosted gating signal being insufficient to turn on theflash cell if the flash cell is in a programmed state; the input stagecomprises an inverter coupled in series with a transistor that iscoupled to the gate of the flash cell, the inverter being coupled toreceive an enabling signal, the transistor to generate the gating signalin response to the enabling signal; the transferring stage comprises: aninverter having an input coupled to receive a transferring signal and anoutput to generate a switching signal in response to the transferringsignal; a p-channel transistor having a gate coupled to receive theswitching signal, a source coupled to receive a voltage supply in therange of 1.65 volts to 2.22 volts, and a drain; and an n-channeltransistor having a gate coupled to receive the switching signal, adrain coupled to the drain of the p-channel transistor, and a sourcecoupled to the drain of the flash cell; and the boosting stage comprisesa capacitor coupled between the gate of the flash cell and a boostingsignal to boost the gating signal on the gate of the flash cell from thevoltage supply in response to the boosting signal.
 51. A fuse circuitcomprising: an input stage to present a gating signal; a boosting stageto boost the gating signal; a transferring stage coupled to receive atransferring signal; a latch coupled to receive data to be transferredby the transferring stage; and a flash cell to hold the data, the flashcell comprising a gate coupled to the input stage to receive the gatingsignal, a drain coupled to the transferring stage, and a source coupledto ground.
 52. The fuse circuit of claim 51 wherein: the input stagecomprises an inverter coupled in series with a transistor that iscoupled to the gate of the flash cell, the inverter being coupled toreceive an enabling signal, the transistor to generate the gating signalin response to the enabling signal; the transferring stage comprises ap-channel transistor coupled between a voltage supply in the range of1.65 volts to 2.22 volts and the latch, and an n-channel transistorcoupled between the latch and the drain of the flash cell, a gate of thep-channel transistor being coupled to a gate of the n-channel transistorto receive the transferring signal, the p-channel transistor to couplethe latch to the voltage supply in response to a low transferring signaland the n-channel transistor to couple the latch to the drain of theflash cell to transfer the data in response to a high transferringsignal; the boosting stage comprises a capacitor coupled between thegate of the flash cell and a boosting signal to boost the gating signalon the gate of the flash cell from a first level of energy based on thevoltage supply to a second level of energy in response to a highboosting signal; the latch comprises an output of a first invertercoupled to an input of a second inverter and the transferring stage andan output of the second inverter coupled to an input of the firstinverter; and the flash cell is enabled to transfer the data to thetransferring stage and the latch when the gating signal is at the secondlevel of energy, the flash cell being turned on by the second level ofenergy if the flash cell is erased and the flash cell not being turnedon by the second level of energy if the flash cell is programmed.
 53. Afuse circuit comprising: a volatile latch circuit to latch data; anonvolatile fuse to hold the data; and a boost circuit to boost a gatingsignal on the nonvolatile fuse to enable the nonvolatile fuse totransfer the data.
 54. The fuse circuit of claim 53 wherein: thenonvolatile fuse comprises a flash cell comprising a gate coupled toreceive the gating signal, a drain, and a source coupled to ground, theboosted gating signal being boosted from a voltage supply in the rangeof 1.65 volts to 2.22 volts, the boosted gating signal being sufficientto turn on the flash cell if the flash cell is in an erased state andthe boosted gating signal being insufficient to turn on the flash cellif the flash cell is in a programmed state; the volatile latch comprisesan output of a first inverter coupled to an input of a second inverterand the drain of the flash cell and an output of the second invertercoupled to an input of the first inverter; the boost circuit comprises acapacitor coupled between the gate of the flash cell and a boostingsignal to boost the gating signal on the gate of the flash cell inresponse to the boosting signal.
 55. A fuse circuit comprising: avolatile latch circuit to latch data; a flash cell to hold the data; anda boost circuit to boost a gating signal on the flash cell to enable theflash cell to transfer the data.
 56. The fuse circuit of claim 55wherein: the flash cell comprises a gate coupled to receive the gatingsignal, a drain, and a source coupled to ground, the boosted gatingsignal being sufficient to turn on the flash cell if the flash cell isin an erased state and the boosted gating signal being insufficient toturn on the flash cell if the flash cell is in a programmed state; thevolatile latch comprises an output of a first inverter coupled to aninput of a second inverter and the drain of the flash cell and an outputof the second inverter coupled to an input of the first inverter; andthe boost circuit comprises a capacitor coupled between the gate of theflash cell and a boosting signal to boost the gating signal on the gateof the flash cell from a voltage supply in the range of 1.65 volts to2.22 volts in response to the boosting signal.
 57. A fuse circuitcomprising: a volatile latch; a nonvolatile fuse; and means fortransferring data from the nonvolatile fuse to the volatile latch.